Increased blastogenic responses to worm antigen and loss of adherent suppressor cell activity after treatment for human infection with schistosoma mansoni

Fifteen Egyptian subjects infected with Schistosoma mansoni were evaluated parasitologically, clinically, and immunologically; treated with praziquantel; and reevaluated nine months later. Fecal egg counts were 97% lower after therapy; seven subjects no longer excreted eggs, as determined by Kato thick smears. Optimal [³H]thymidine incorporation induced by soluble adult worm antigenic preparation (SWAP) in peripheral blood mononuclear cells (PBMCs) increased significantly, from 4, 041 ± 434 (mean change in cpm ± SE) before treatment to 11, 232 ± 3, 414 after treatment (P <.0005). The relation between dose of antigen and response also shifted; the SWAP concentration producing optimal responses was 30.0 µg/ml before and 1.0 µg/ml after therapy. Before treatment, depletion of adherent cells from PBMCs in six subjects resulted in enhancement of responses to SWAP from 5, 575 ± 1, 210 to 14, 719 ± 8, 190 (P <.025). However, in these same individuals after treatment, PBMC and nonadherent lymphocyte responses were similar (22, 917 ± 6, 505 and 21, 239 ± 6, 122). These studies indicate loss of activity of adherent suppressor cells after treatment of chronic infection with S. mansoni. Waning of cellular regulatory mechanisms as the parasite load decreases may contribute to restoration of blastogenic responses.